| Wetlands on the Earth are richer in biodiversity and unique ecosystems and there are richer in natural resources. Wetlands is not only a natural gene pool of the species, the protection of the Earth, many rare and endangered plants and animals, but also have lots of ecological effects, including homogenization flooding, conservation water sources to prevent soil erosion and regulation climate, degradation the pollutants in the environment, which has known as the Earth's "kidneys". A variety of wetlands in Huliu River Nature Reserve in Guangling, Shanxi, distributes widely and has the rich biodiversity. There are Glycine soja in the reserve, being National 2nd level of protections plants.Based on the dataset including 70 plots from the field, the classification and ordination of wetland plant community in Huliu River Nature Reserve were studied by using TWINSPAN and DCA. The 70 plots were divided into 14 groups by TWINSPAN, which belong to 14 Associations according to the principle of vegetation classification of China. The result from DCA ordination for the plots reflected the relationship between plant community types and the environment gradients, and it showed that the distribution pattern of those communities were mainly dominated by the leading ecology factors, including humidity and content of organic matter. The DCA ordination of 20 dominants showed that the species acted as an indicator for habitat factors and was impersonally reflected characteristics of biotope. The ordination of dominants was similar to the classification of community types, reflecting the change trend of the community type and the species distribution with changing environmental factors.The niche breadth and niche overlapping of dominant populations of the communities were studied by using Shannon-Wiener index and Portraits's methods. The results were that:Phragmites communis, Inula japonica, Scirpus yagara, Glycine soja, and Plantago asiatica were able to adapt to the environment well and had more effective capability to use the resource and took up more advantage status in competition because of their wider niche. However, Lemna minor, Nymphoides peltatumand Triglochin palustre had weak adaptability to the environment, and their utilizing resources was relatively lower and narrower distribution owing to narrower niche. There was not absolutely general overlapping among 33 dominants. There were overlapping significantly for 87 species-pairs, accounting of 7.39% in the total species-pairs, and showing that there were some common adaptive to environment. It suggested that those 33 species did not show a significant niche overlap completely universal, all kinds of inter-group differences in the use of resources was still significant, indicating that population trends of resource sharing was not clear, the community in a relatively unstable. The correlation analysis between niche breadth and species frequency showed that it was positive correlation (r=0.880, P<0.01), indicating that the niche breadth depends largely on the frequency of species.The patterns of dominant populations of the communities were studied by using v/m (dispersal index) ratio t-test, clump intensity, mean crowding, Green's index, intensity index,χ2-test for goodness-of-fit for Poisson distribution and negative binomial distribution, respectively. The results showed that the patterns of those populations were all clumped; however, they were different in clump intensity. Moreover, the result suggested that the application of variance/mean ratio and its t-test together was one kind of fairly good method to analyze population patterns, and mean crowding can be used to study clump intensity of population patterns.
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